You mention that additional challenges must be met since the battlefield was in continual motion, which obviously would make the assessment of each regimental position even harder to determine. This I feel is not quite true.
Of course I agree that “formations changed according to movements, threats, losses and circumstances”.
But I do not conclude that from MacDonalds report that parts of Broussier and Lamarques divisions were in line before the assault (this makes me wonder what kind of lines you are referring to when they were formed). In my opinion both Broussier and Lamarques were formed in accordance to the system (doctrine) of 1805; and the system works much better than to just say, a body of troops filled in where there was a weak link to the great body of troops.
There was actually a formula that was built and it worked. There was a point and purpose to each countries military system.
Generals just didn’t make up their own "minor tactics" which comprises all the details for the formation, instruction and exercise of a battalion, a squadron, a regiment, which also comprised the sovereign ordonnance, and subordinate systems.
Nor would a general make up his own "grand manoeuvres" which encompasses all the great features of war, such as the deployment of armies, orders of march, orders of battle, to include the science of choosing positions and knowing the terrain. All this was brought together to create a military system or what we call military doctrine today.
Just look at Oman, he was a great historian, but he knew very little of military science and absolutely nothing of the British and French ordonnance, their general principles or military systems, and because of this he caused great damage in his explanations of certain events.
I have read astonishing postulation from authors who have attempted to elucidate how in a battle, a manoeuvre, an evolution, or a compound evolution was executed, without a sound knowledge of military science, or of the particular military system being explained.
Take your example of Colonel Penne's report:
"La division marchait la gauche en tête; le régiment formait le tête de colonne et marchait sa droite appuyée derrière la droite du 92e, qui marchait en bataille."
So what does this tell us, it tells us that when Severoli arrived the 112e was leading otherwise it would have been the 1er de ligne italien who would have lead the division, par la droite en tete. This also supports my theory, which is in accordance to the French military system, when I said that the 92e and 92 bis were deployed in the Colonne Vuide.
Since Colonel Penne reports that his regiment was leading the column, it would be safe to assume that they were coming up on the right side of the Colonne Vuide. Of course everything is conjecture, but it is based upon my understanding of the French military system.
As for casualties, I mentioned that perhaps I was digging too deep in the weeds, for just a general estimation. Nevertheless when most casualties are from musketry, the formation, ratio of officers, and their position does make a difference in ballistic evaluations. However when you adjust for artillery casualties, then I would agree with you, for everything depends upon where the ball lands...